Olympic baseball is governed by the International Baseball Federation.
International Baseball Federation The IBAF is the worldwide governing body for the sport, sanctioning games and setting the rules for games between teams sponsored by the national baseball federations of member countries. Its major tournaments include the Baseball World Cup, the World Baseball Classic (the only tournament in which major league players play), the Intercontinental Cup and the Olympic baseball tournament (in conjunction with the International Olympic Committee).
USA Baseball It was founded in 1978 and is the governing body for amateur baseball in the United States of America. USA Baseball is a member of the U.S. Olympic Committee. USA Baseball and MLB work in tandem to select Team USA for both the World Baseball Classic and the Olympic Games.
United States Olympic Committee The USOC supports American athletes in general and Olympic athletes in specific and selects and enters athletes for participation in the Olympics. The committee provides training centers, funds, and support staff to elite athletes. For baseball, much of the responsibilities are handled by USA Baseball.
International Olympic Committee The IOC organizes the Olympic Games held in Summer and Winter, every four years. In a controversial move, the IOC has ruled that baseball and softball will not be played in the Olympics in 2012 because it's not played by enough countries.